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Abstract:

Palladosilicide, Pd2Si, is a new mineral (IMA 2014-080) discovered in chromite-rich samples from the Kapalagulu intrusion, western Tanzania (300351E 55316S and 300537E 55426S) and from the UG-2 chromitite, Bushveld complex, South Africa. A total of 13 grains of palladosilicide, ranging in size from 0.7 to 39.1 m (equivalent circle diameters), were found. Synthetic Pd2Si is hexagonal, space group P62m, with a = 6.496(5), c = 3.433(4) A, V = 125.5(1) A3, c:a = 0.529 with Z = 3. The strongest lines calculated from the powder pattern (Anderko and Schubert, 1953) are [d in A (I) (hkl)] 2.3658 100 (111); 2.1263 37 (120); 2.1808 34 (021); 3.240 20 (110); 1.8752 19 (030); 1.7265 12 (002); 1.3403 11 (122); 1.2089 10 (231). The calculated density for three analyses varies from 9.562 to 9.753 g cm-3. Palladosilicide is considered to be equivalent to synthetic Pd2Si based on results from electron backscattered diffraction analyses. Reflectance data in air for the four Commission on Ore Mineralogy wavelengths are [ nm, R1(%) R2(%)] 470 49.6 52.7; 546 51.2 53.8; 589 51.6 53.7; 650 51.7 53.3 and the mineral is bright creamy white against chromite, weakly bireflectant and displays no discernible pleochroism or twinning. It is weakly anisotropic, has weak extinction and rotation tints in shades of blue and olive green. Electron probe microanalyses of palladosilicide yield a simplified formula of Pd2Si. 2015 Mineralogical Society 2015.

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Compilation and indexing terms, Copyright 2018 Elsevier Inc.<br/>20154501511890<br/>Bushveld Complex<br/>Kapalagulu intrusion<br/>New mineral<br/>Palladosilicide<br/>Platinum group elements<br/>Platinum group minerals<br/>South Africa<br/>Tanzania<br/>UG-2